(单选题)5: In August, it is very hot and wet in the southern part of the United States. People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot at some times and cold at other times. People in these states will have heart trouble after the weather changes in February or March. The weather can also influence intelligence. For example, in a 1983 study by scientists, the IQ scores of some college students were very high during a storm, but after the storm, their scores were low. Storms can increase intelligence. Very hot weather, on the other hand, can lower it. Students in many schools of the United States often do badly on exams in the hot months of the year (July and August). Weather also has a strong effect on people＇s feeling. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel depressed during cold weather. In hot summer weather, on the other hand, fat people may feel unhappy. At about 65℉, people become stronger. Low air pressure makes people feel free, but it also increases forgetfulness. People leave more bags and umbrellas on buses and in stores on low pressure days. There is a “perfect weather” for work and health. People feel best at a temperature of about 64℉ with 65 percent humidity. Are you feeling sick, sad, tired, forgetful, or very intelligent today? The weather may be the reason. 问题： Intelligence may increase during（ ）.
A: a perfect weather
B: a storm
C: very hot weather
D: low air pressure
